This invention relates generally to forage harvesters, and specifically to an improved shear bar which reduces crop material movement therealong during the shearing operation and, therefore, promotes more uniform wear characteristics.
Generally speaking, a forage harvester includes at least a pair of opposing infeed rolls which transfer crop material in a ribbon-like mat across a shear bar into engagement with a rotating cutterhead having a multiplicity of knives thereon. The more sophisticated forage harvesters in commercial use today employ a cutterhead with spiral-like knives thereon which move across the stationary shear bar at an angle, thus shearing the crop material as opposed to chopping it. It has been found that the shearing action causes the knives to engage the mat of material and move it slightly toward the trailing edge of the knife. This movement of material results in a build-up along the edge of the shear bar which cooperates with the trailing edge of the knife. Since the crop materials being acted upon are quite abrasive, the prior art shear bars wear unevenly, i.e., the end of the shear bar nearest the trailing edge of the knife wears much more quickly than the remainder. Since uneven wear of the shear bar results in a reduction in overall machine efficiency which cannot be "adjusted out" the shear bar must be periodically reversed or replaced more often than an even wear situation would require.
The invention to be described below reduces the ability of the crop material to move along the shear bar, and thus greatly reduces the uneven wear characteristics heretofore known.